Exercise 1 Page 41

Finding the Slope and y-intercept

One way to use a graph to find the slope of a line is to count out the change in x and y.

As the graph travels from left to right, the rise, or change in y, is 200. Similarly, the run, or change in x, is 1. slope=rise/run ⇔ m=200/1=200 The y-intercept is the point where the line crosses the y-axis. Looking at the graph, we can see that the y-intercept is . With these values, we are ready to complete our equation. y= 200x+ ⇒ y=200x

Interpreting the Graph

Finally, we can interpret the information that we can learn from the graph.

• Slope: A slope of 200 tells us that the balance in the bank account increases by $200 each week.
• The intercept: A y-intercept of 0 means that the beginning balance in the account was $0.